MORPHOLOGY OF ANGIOSP^RMS. 



133 



and the petals are convolute. Furthermore, in addition to the 

 principal types of estivation and vernation already given, there 

 are a number of special modifications of these, depending upon 

 the number and arrangement as well as direction of the over- 

 lapping parts of the flower- or leaf-bud. 



A B 



Fig. 84. Types of flowers: A, hypogynous flower of flax; B, perigynous flower of 

 cherry, showing perianth tube with sepals, petals and stamens on its border; C, epigynous 

 flower of American sarsaparilla; D, flower of buttercup showing apocarpous gynscium 

 and large conical torus; E, irregular (bilateral or zygomorphic) flower of aconite 

 showing half of helmet-like sepal (a), other sepals (b, c), long-clawed nectary (k) developed 

 from one of the posterior petals, separate pistils (f); F, corolla of Salvia spread open and 

 showing the two rudimentary stamens and two fertile stamens. The connectives in the 

 latter are long and filamentous and each bears at the upper part a normal pollen sac and 

 at the lower end a non-fertile enlarged portion which the insect pushes againr.t in entering 

 the flower and thus causes the pollen to be deposited on its back. A-C, after Gray; D-F, 

 after Warming. 



